Combined frequency changer and phase converter



Dec. 14 1926.

R. E. HELLMUND I COMBINED FREQUENCY CHANGER AND PHASE CONVERTER Filed Anril 26.

INVENTOR Rudolf E. Hellmund.

a BY M AT TORNEY 1m s or.

' eci to, i loo,

RUDOLF E. I-IELLIM'UND, 01F SVVISSVALE.

LE-IC'UFSE ELECTRIC MANUFACTUEEFTIG CGMPAHY A VANIA.

COMBIXED FREQUENCY CPEANGEB PITUESE GGNVEBTER.

Application filed 5.]. 2o,

My invention relates to alternating-cue rent dynamo-electric machines and it has special reference to combined frequency changing and. phase converting niaciiines which are particularly adapted for use upon electric railway locomotives.

The prinoi al object of my invention is to provide a novel frequency changer and nh'aso onverter wh ch is adapted to supply oower from a single-phase alternating-cur- 'rent source to a polyphase motor means or aggregate and which is particularly suitable for use in electric locomotives.

A more specific object of my invention is to provide a combined frequency changer and phase convertr of the ahove-inentioned type, having; a single stationary magnetic core anc. a single rotating .iuae'netic core, and to provide windings adapted for simultaneous operation on. two pole numbers.

it well known that locomotives employed on alternating current railway systems are best operated by means of low-frequency poly'phase motors or motor ao' 'regates. The

fix .insmission of powa' to such locomotives is, however, most ad"iantan'eously effected by u'ieans of single-phase alternating! currents r andard commercial frequency. ch frccnency, for instance that of the 60 cycle sy em" is considerably higher than the desired motor frequency. l Vith growing; elec rification of the railway systems of this and other countries. reasons of economy and service maize it increasingly important to i e t of employing the standard commercial frequency for railway operation. Accordingly, the provision of su table a ipa atus permitting the construction of ice ives supplied by standard-frequency cu rents and driven by low-frequency pelyphase motors will have a decisive influence upon the rate at which electric opera tion of the railways will he adoptec.

l have devoied a great amount of study and have c nducted numerous investigations in an. endeavor to provide a f: quency (-ll l phase converter which meets the uts of raiiway service and I have found that by the use of a combined wind- 1922. Serial No. ing adapted for operation on two pole numhers a. very simple and eilicient machine may he designed which meets the requirements in question.

My invention will best he understood by reference to the, accompanying drawings, wherein- Figure 1 is a diagrammatic view of a drivin system of an electric locomotive embody in my invention.

2 is a curve diagram of certain operat inc; characteristics of my frequency changer.

Fig. 3 is a winding; diagram showing a development of the stator windine used in the frequency changer illustrated 1n Fig. 1.

In the system shown in Fig. energy is supplied from a single-phase high-voltage line 3 operating with. a standard commercial frequemiy. say 60 cycles, through a transformer 2 and an alternating current converter 3a, to a low-frequency polyphase motor means or aggregate 4t. propelling a locomotive. I have shown. for purposes of illustration, an induction motor 5 controlled by a secondary liquid rheostat 6 and driving a locomotive wheel 7.

The converter 3o. consists of a stator 8 and. a rotor 9 which may he of a standard induction-motor construction. The stator is shown as being provided with a special coinhined winding; -11. 11, 11, which is designed for simultaneous operation with two pole numhers corresponding; to the two fr qucn cies, the supply iirequency say cycle. and load frequency one-sixth as great, said stator winding furthermore permitting single phase operation with the la er pole numher and polyphase operation with the smaller pole numher.

7 My combined winding; for simultaneously carrying the currents of both frequencies in conformity with the ahove-stated requirements consists of three winding groups 11. 11, 11 corresponding; to three phases of the motor aggregate i. The winding-group 11 consists of four coils or coil-groups I, II, III, IV having terminals A, a. for low-frequency operation and. intermediate ter int nals B, o, for higlrfrequency operation.

connected to se of the stator winding.

The other winding groups 11 and 11 are similarly constructed, the composite parts being appropriately indicated by prime marks and seconds. In the drawing, the low-frequency terminals A, a; A, a and A, a, respectively, are shown star connected to the load 4:. The high frequency ter- Ininals B, b; B, Z) and B, 2'), corresponding to the respective winding-groups, are parate secondary windings on-the single phase transi orn er 2.

The rotor 9 is provided with two wii 1- ings, a close-circuited winding 12, which may he of the squirrel-cage type, and a direct current exciting winding 13, which is preteraloly wound for the smaller pole number and so designed as to he unalfected by the high-frequency rotating field. The directcurrent exciting winding may, however, he a double-pole-number winding, or other means may he adopted for securing sy chronous operation on the hi gh-trequency side as well as on the low-frequency side. lt-will he understood, of course, that the precise details of the means for performing the functions of the windings l2 and are not essential to my invention, its broadest aspects.

The single-phase winding connection ot thestator, supplied from the high-frequency source causes the machine to operate as an induction motor in conjunction with the close-circuited rotor winding 12, the rotor having a speed corresoonding to the higher pole number of the single phase connections I Th direct-current excited winding 13 of the rotor then induces, in the polyphase winding terminals A, a, A, a" and A", a, alternating currents having a low frequency corresponding to the smaller pole number.

The motor and generator currents fiowing in the stator windings 11 will, in general, he oppositely directed and consequently acancell'ation of the currents, will be etlected resulting in a reduction of the losses, and a correspondingly high eific'iency of the ma chine, as will he hereinafter more fully explained.

Theflux distribution is shown in. Fig. :2, wherein the curve Y shows the twelve-pole field produced by, or corresponding to, the high-frequency connections B, Z); B, Z) and B, Z). The two-pole field of the directcurrent exciting winding 13 is shown at X. and the resultant total field is shown at Z in Fig. 2. I Y

The stator winding ll, 11, 11., of which one phase, 11, is shown in development in Fig. 3, is wound in twelve slots, corresponding to the number of poles of the high-irequency connections. In accordance with my invention, the stator inductors are connected in coils orcoil- 'roups ll, lull, IV; I, II, III, IV; I", I, Hi, IV, each coil or coil group having a pitch equal to (2N +1) times the pole-pitch of the higher pole number, where l? is any integer, clependent upon the trequency ratio and other conditions desired. It is not essential that every coil. shall have exactly the pitch tated, so long, as the desired pitch is approximated. ln the preferred form or my invention, a sixto-one frequency ratio is obtained with a coil-pitch exactly five tunes the high-frequency pole-pitch, N being equal to :2.

Another characteristic of my invention is n which thecoils are connected example, thecoils I, H, 111, IV of e windinggroup 1.1. l he second coil ll disposed one high-frequency pole-pitch in vance of the first coil l. The third coil is started in the same slot as the last "i185 from the first coil 1, and it will i that 2(l'l-l-l} is the frequency ratio N-l-l) is the number of phases of the requency winding. l he tourth'coil IV is disposed one hieh-trequency pole-pitch in advance of the third coilv Ill. l he coils closed circuit in the order phase shift of 2(N+l) high-frequency are connected in a l-lllV l, with the coil chains I-1I and lll?f in parallel torthe lowireruency connections, and the coil chains l ill and ll ll in parallel for the highl requency connections, shown in l and The other two phases or windingg'roups 11 and ll are displaced from the winding-group ll by 60 or 120 electrical degrees or the low-frequency field, as will be --oo by those skilled in the art. 0; e"ation, since there are twelve equispaced sl ts and twelve equi-spaced poles, the twelve-pole component Y or the field i lures an instantaneotie-voltage or the same inagrnituce in each of the inductors or coil-sides of the primary windings 11, v1, 11, regardless of the relative phases of thetwo-pole field and the SlTi-DOlQ field. Voltages of three different magnitudes, as indicated at 0),, cc, and in 2, are simultaneously induced 'in the several coil sides reason of the two-pole component X of the field, the lirections ot the induced voltagesheing indicated on the winding development in Fig. 3.

An inspection oi the drawing will show t. it, with the construction 'hereinahove de .crihed, the instantaneous ialue of the total volt-age induced in the coil-chain l-ll is c :2rc,-{-w m the con'iponents due to the twelve-pole field cancelling'ont. The in -n taneous v hie of the total voltage induced the coil-chain l-lll is c zg the components due to the two-field cancelling; out.

s in the resp ciive phaces windticular frequency-ratio of 6:1 as de high-frequency voltages 0]"; all the phases are c z ly/ at the same instant, and hence single-phase operation is necessary'with the high-ih'equency connections and with the parcribed.

It will be noted that my winding is chorded to have a coil pitch equal to fivesixths of the pole-pitch with respect to the smaller pole-number, and that the coils are not connected in consecutive order, but in the order l:-II1VIII. It will further be noted that, while I have shown a simple embodiment utilizing only one slot per pole of the large pole number, it is obvious that the coil sides may be distributed over a plurality of slots per pole.

Aside from the transformation from single-phase high-frequency power to threephase low-frequency power, which is particularly useful for railway electrifications, my invention has, for one or its chief advantages, the provision of a transforming means in which the electric currents largely neutralize each other in the windings. ihus, the motoring currents drawn from the high frequency line oppose the induced electromotive forces y, in the respective inductors, while the generated low-frequency currents are in the same direction as the generated voltage as and 50 and opposite to the gen erated voltage e2 At the particular instant illustrated in the drawing, therefore, the input and output currents are in opposition, with a resultant neutralizing or cancelling action, in four out of the eight coil-sides shown in phase 11 in Fig. 3, therel y indicating a. material reduction in the heating the composite stator winding 11,

losses in 11, 11".

While the following claims refer to a machine in which the low-trequency winding has two poles, the language is intended to comprehend the multiplication of the winding in machines in which the smaller pole-nu1nber is four, six, eight, etc.

Those skilled in the art will recognize that my invention is susceptible of numerous modifications and is also adaptable to other applications than to railway locomotives. I accordingly, desire that only such limitations shall be imposed thereupon as are set forth in appended claims.

I claim as my invention:

1. In a dynamo-electric machine, a winding comprising at least two coils per pole, the coils being serially conn cted in the order l-lllV-Ill, where coils I and II are under one pole and coils Ill and IV are corresponding coils under a pole of opposite polarity.

2. A dynamo-electric machine winding having an (Nl1) phase, low-frequency connection and at the same time having singlephase, high-frequency connections of approximately 2(N+1) times the frequency of the lowdrequency connections, where N is an integer greater than. Zero, said winding comprising a number of coils equal to the pole-number of the high-frequency connection and having a coil-pitch approximating (ZN-l-l) times the pole-pitch of the larger pole-number, the first two coils under the north pole of the iow-itremiency connection being permanently connected in series and being paralleled by the first the south pole ot said low-frequency connection, thereby providing a group of tour coils. the remaining coils being similarly connected in groups of tour coils each. the

groups being connected in an (N+l) phase circuit for low-frequency operation, and two intermediate connections between the coils in each group to provide a plurality of single-phase circuits for higlrirequency operation.

3. A dynamo-electric machine having a winding for simultaneous single-phase operation on a large pole number and polyphase operation on a small pole number, said winding comprising a plurality of coils corresponding in number to the larger number of poles and having a pitch equal to an odd multiple ct the pitch of said larger pole number, said coils being connected into polyphase groups having terminals for deriving substantially balanced polyphase currents corresponding to the lower number of poles, each group corresponding to one of said phases, and terminals for deriving from each of said groups ill-PlluSB single-phase currents corresponcmg to the smaller pole-number.

e". A double-pole-number dynamo-electric machine comprising a winding disposed in the same number of slots as the larger polenumber, whereby single-phase operation is obtained with the larger pole-number, and polyphase operation is obtained with the smaller pole-number, each phase of said winding. considered from the standpoint of the smaller pole-number, comprising at least two coils per pole, the coils being serially connected in the order III IVIII, where coils I and H are under one pole and coils Ill and IV are corresponding coils under a pole of opposite polarity.

In a dynamoelectric machine, a threephase winding each phase comprising a pair of coils per pole, said coils having a throw of live-s. 15 ot the pole-pitch, the coils of each pair being displaced by one-sixth of the pole-pitch, the coils 01" each phase being serially connected in the order lIIIIV- Ill. where coils I and II are under one pole and coils Ill and IV are corresponding coils under a pole of opposite polarity.

(3. Ll; double-pole-number winding for a double-current machine having a six-to-one frequency ratio, comprising a plurality of coils having a coil-pitch approximating five times the pole-pitch of the larger polenumtwo coils under 4 ber, successive coils being displaced by one pole-pitch of the larger pole-number, said coils being connected in three phases corresponding to the smaller pole-number, each oi said phases, considered from the standpoint of the smaller pole-number, comprising at least two coils per pole, the coils being serially connected in the oroer IllIV' Winding, said Winding comprising a plurality of coils each having a pitch of five times the pole-pitch of the larger pole-number, successive coils being displaced by one polepitch of the larger pole-number, said coils being connected in three phases corresponding to the smaller pole-number, each of said phases, considered from the standpoint of: the smaller pole-number comprising at least two coils per pole, the coils being serially connected in the order llllVlll, Where coils I and II are under one pole and coils HI and IV are corresponding coils under a pole of opposite polarity, and terminal connections for operating the coil chains III and III-IV in parallel for the lowfrequency connections, and the coil chains IIII and II- IV in parallel for the high frequency connections, polyphase connections for said low-frequency terminal connections, and a transformer having three equal insulated winding sections for the high-frequency terminal connections of the respective phases.

8. A frequency-changing system having a siX-to-one frequency ratio, comprising a dynamo-electric machine having a composite Winding, said Winding comprising a plurality of coils each having a pitch of live times the pole-pitch of the larger pole-number, successive coils being displaced by one polepitch of the larger pole-number, said coils being connected in three phases corresponding to the smaller pole-number, each of said phases, considered from the standpoint of the smaller pole-number, comprising at least two coils per pole, the coils being serially connected in the order l-lL-rV-lll, Where coils I and H are under one pole ant coils III and IV are corresponding coils under a pole of opposite polarity, terminal connections for operating the coil chains l ll and Ill-IV in parallel for the lowtrequency connections, and the coil chains ll1l and ll-lV in parallel for the hightrequency connections, a secondary Winding smaller polenumber, polyphase connections for said low-frequency terminal connections,

.nd a transformer having three equal insuated Winding sections for the high-treiuency terminal connections of the respecivc phases.

9. In a dynamo-electric machine, a three phase Winding, each phase comprising a pair of coils per pole, said coils having a throw of live-sinths oi the pole-pitch, the coils of sch pair being displaced by one-sixth of the ie-pitch, the coils of each phase being selly connected in the order lllIVIlI,

l. u iere coils I and H are under one pole and coils ill and IV are corresponding coils uner a pole of opposite polarity, and interr rte connections for each phase for obrng a dii'lerent pole number.

a. in a dynamo-electric machine, the combination of a stationary magnetic core and a rotating magnetic core, windings dispo ed on one of said cores and adapted to operate with two differentpole numbers, other windings disposed on the other of d cores to operate simultaneously singlepnase on one 'requency and polyphase on another frequency.

11. ll dyna ']0Ql8Cl'/ll(3 machine for conx 'erting currents of one frequency into currents of another frequency comprising a com bined Winding responsive to two different pole numbers having an even pole-number ratio, a of single-phase terminals upon said winding responsive only to the eilifects of a field corresponding to one pole number, and a set of polyphase terminals upon said winding responsive only to efiects of a field corresponding to the other pole number, said windings comprising a plurality of coils having a pitch substantially equal to a multiple of the pole pitch of the large pole number, said coils being shifted against each other by a distance substantially equal to said pole pitch.

12. A combined frequency-changing and phase-converting machine comprising a stationary core and a rotating core, a combined Winding upon one core adapted for simultaneous operation with two pole numbers having a ratio oi": 6:1, said winding comprising coils hea ing a pitch equal to five times the pole-pitch of the larger number of poles and spaced apart by a distance equal to said pole-pitch, a set oi single-phase terminals upon said Winding responsive only to the effects of a field corresponding to the larger number of poles and a set of polyphase terminals disposed iinermediate said single-phase terminals and responsive only to the effects of a field corresponding to the sr all number of poles.

13; In a dynamo-electric machine, a Winding adapted for simultaneous operation with two pole-ninnbers having a ratio of 6: 1, said Winding comprising coils having a pitch equal to. live times the pole-pitch of the larger number of poles and spaced apart at a distance equal to said pole-pitch, terminals and intermediate terminals upon said Winding, permitting the simultaneous operation of said Winding in connection with polyphase low-trequency currents and single-phase and relatively high-frequency currents. 16

In testimony whereof, I have hereunto subscribed my name this 20th day of April 1923.

RUDOLF E. HELLMUND. 

